The most common and desirable way to deliver active pharmaceutical ingredients (APIs) is in the crystalline form. APIs can be formulated in pure form, as salts, or as multicomponent (solvate, cocrystal) solids and these offer due to stability and processing advantages over other formulations. The choice among these forms depends very much on the specific chemical properties of the drug molecule as well as factors such as solubility. However, there is the pervasive issue of crystal polymorphism to consider: a given composition is not constrained to crystallize in a predictable way and multiple packing motifs of the same unit possess different thermodynamic stabilities that can influence bioavailability. The proposed program will develop more rapid and comprehensive techniques to control the crystallization of bioactive organic molecules while being less material intensive. Thi will enable early stage screening of potential drugs to determine which form has the appropriate solubility and stability to be formulated into a bioavailable dosage. Three interconnected aims are designed to develop and deploy more efficient and robust polymorph discovery methodology. Aim 1 adapts the polymer-induced heteronucleation (PIHn) approach towards solid form discovery so that it functions in a high throughput manner suitable for polymorph discovery. Two of the key advances proposed are miniaturization of the technology and automation of the solid form screening, which together will make the PIHn method much better suited for the screening of preclinical drug candidates. Aim 2 addressed the issue of crystal polymorphism outside of the well-studied realm of neutral molecular compounds. Because solvates, salts, and cocrystals are increasingly the solid forms of choice for drugs entering the clinic, there is a pressing need for understanding solid form diversity in such APIs. The methodology proposed in Aim 1 is perfectly suited to polymorph discovery in solvates, salts, and cocrystals because it can generate solid form diversity even under the relatively narrow sets of conditions employed in multicomponent crystal formation. Finally, in Aim 3 a new strategy for identifying targeted inhibitors of crystal forms will be introduced. The approach involves a new paradigm, based on the mechanistic understanding of how PIHn accelerates nucleation, redeployed for creating soluble polymeric nucleation inhibitors.